1. Field
The field relates to an organic light emitting display and a fabricating method thereof, and more particularly to an organic light emitting display and a fabricating method wherein a color of a pixel can be determined based on a distinctive pattern of an element of the pixel. The pattern may, for example, be in at least one of a lower electrode of the capacitor and an anode. Consequently, a cause of a pixel defect can be determined more easily.
2. Description of the Related Technology
In general, an organic light emitting display is a device wherein light is generated as an electron and a hole combine with each other near a fluorescent or phosphorescent chemical compound by injecting a hole into an anode and an electron into a cathode.
As shown in FIG. 1, the organic light emitting display is basically composed of an anode (ITO: Indium Tin Oxide), an organic thin film, and a cathode e(Metal). The organic thin film may include an emitting layer (EML) which generates light by forming an exciton as an electron and a hole meet each other, an electron transport layer (ETL) transporting an electron, and a hole transport layer transporting a hole. Additionally, an electron injecting layer (EIL) can also be formed on one side of the electron transport layer, and a hole injecting layer (HIL) can also be formed on one side of the hole transport layer.
A passive matrix method and an active matrix method are well known driving methods for driving the organic light emitting diode. The passive matrix method has advantages in that the fabricating process is simple, and the investment is small because an anode and a cathode are formed so that they cross each other in an orthogonal direction. In addition, the organic light emitting diode is driven as a line is selected. However, it also has disadvantages in that the current consumption can be large when an image is displayed on a large size display. The active matrix method is beneficial in that the current consumption is small, the image quality is excellent, the lifetime is long, and it can be a medium large size because an active element and a storage capacitor such as a thin film transistor are formed for each pixel.
A fabricating method of the organic light emitting display may include a crystallization step of amorphous silicon, a step of manufacturing of an active layer (a thin film transistor and a lower electrode of the capacitor), and a step of manufacturing of an organic light emitting diode. There are other steps such as an encapsulation step and a module assembly step. However, the description about these steps will be omitted.
The crystallization step of amorphous silicon may include a substrate cleaning step, a buffer layer forming step, an amorphous silicon evaporating step, and a poly silicon forming step and so forth.
In addition, the step of manufacturing of an active layer includes a step of patterning the poly silicon, a step of forming a gate insulating layer, an ion injection/activation step, a step of forming an interlayer dielectric layer, a step of forming a contact hole, and a step of patterning of source/drain electrode and so on. A step of forming an insulating layer and via, a step of forming an ITO, and a step of forming a pixel definition layer are executed additionally.
Meanwhile, in the fabricating method of the organic light emitting display, an inspection step is executed to detect inferior goods which does not show an excellent emission characteristic. It can take much time to determine a cause of a defect accurately, thus, productivity can be decreased.
In a high resolution organic light emitting display, an undesirable short circuit may happen because a distance between adjacent wires decreases, which is an important cause of a defect. Accordingly, a lighting test and so forth can be executed to determine at which region from among a RGB pixel an undesirable short circuit which can be a cause of a defect happens.
Conventionally, in case that the aperture ratio of a pixel generating red, green, and blue light is the same, a diode evaporated on a substrate is formed so that the same pattern is formed at each RGB pixel. Accordingly, before an organic material is evaporated, RGB cannot be distinguished with the pattern. Consequently, it has a disadvantage that it takes much time to determine a cause of a defect accurately.